1. Field of the Invention
The present invention relates to physiologic monitoring and/or therapy. Although embodiments make specific reference to monitoring impedance and electrocardiogram signals with an adherent device, the system methods and devices described herein may be applicable to many applications in which physiological monitoring and/or therapy is used for extended periods, for example wireless physiological monitoring for extended periods.
Patients are often treated for diseases and/or conditions associated with a compromised status of the patient, for example a compromised physiologic status. In some instances, a patient may report symptoms that require diagnosis to determine the underlying cause. For example, a patient may report fainting or dizziness that requires diagnosis, in which long term monitoring of the patient can provide useful information as to the physiologic status of the patient. In some instances a patient may have suffered a heart attack and require care and/or monitoring after release from the hospital. One example of a device to provide long term monitoring of a patient is the Holter monitor, or ambulatory electrocardiography device.
In addition to measuring heart signals with electrocardiograms, known physiologic measurements include impedance measurements. For example, transthoracic impedance measurements can be used to measure hydration and respiration. Although transthoracic measurements can be useful, such measurements may use electrodes that are positioned across the midline of the patient, and may be somewhat uncomfortable and/or cumbersome for the patient to wear. In at least some instances, the electrodes that are held against the skin of the patient may become detached and/or dehydrated, such that the electrodes must be replaced, thereby making long term monitoring more difficult.
Work in relation to embodiments of the present invention suggests that known methods and apparatus for long term monitoring of patients may be less than ideal. In at least some instances, devices that are worn by the patient may be somewhat uncomfortable. Although devices that adhere measurement electrodes and measurement circuitry to the skin with an adhesive can provide improved comfort, work in relation to embodiments of the present invention suggests that the adhesive of such devices can detach from the skin of the patient sooner than would be ideal. These limitations of current devices may lead to patients not wearing the devices as long as would be ideal and not complying with direction from the health care provider in at least some instances, such that data collected may be less than ideal.
Similar difficulties may arise in the monitoring of other subjects, such as persons in non-medical settings, or in the monitoring of animals such as veterinary, agricultural, or wild animal monitoring. Therefore, a need exists for improved subject monitoring. Ideally, such improved subject monitoring would avoid at least some of the short-comings of the present methods and devices. Ideally, such improved devices will allow an adherent device to be adhered to the skin of the subject with an adhesive so as to carry associated electronics comfortably with the skin of the subject for an extended period.
2. Description of the Background Art
The following U.S. Patents and Publications may describe relevant background art: U.S. Pat. Nos. 3,170,459; 3,805,769; 3,845,757; 3,972,329; 4,141,366; 4,522,211; 4,669,480; 4,838,273; 5,133,355; 5,150,708; 5,450,845; 5,511,533; 5,607,454; 6,141,575; 6,198,955; 6,327,487; 6,795,722; 7,395,106; 2004/0006279; 2004/0015058; 2006/0264730; 2007/0106132; 2007/0208262; 2007/0249946; 2007/0255184; 2008/0171929; 2007/0276273; and 2009/0182204.